1. Field of the Invention
The present invention relates to a status detector for a power supply, a power supply, and an initial characteristic extracting device for use with the power supply, each of which is suitable for detecting the status of a battery (accumulator).
2. Description of the Related Art
In power supplies, decentralized power storages, and electric vehicles using electricity accumulating units such as a lithium secondary battery, a nickel-hydrogen battery, a lead-acid battery, and an electric double-layer capacitor, a status detector for detecting the status of each electricity accumulating unit is employed to ensure safe and effective use of the electricity accumulating unit. The status of the electricity accumulating unit includes, e.g., the state of charge (SOC) or the remaining capacity indicating to what extent the unit is charged or how much dischargeable charges remain, and the state of health (SOH) or a deterioration level indicating how fat the unit is deteriorated or run down. In order to detect those states of the electricity accumulating unit, it is also required to know characteristic information (such as internal DC resistance) of the electricity accumulating unit beforehand.
SOC (State Of Charge) of a power supply used in portable equipment, electric vehicles, etc. can be detected by integrating current discharged from the fully charged state and calculating a ratio of the amount of charges remaining in the electricity accumulating unit (i.e., the remaining capacity) to the amount of maximally chargeable charges (i.e., the fully charged capacity). In many of the electricity accumulating units, however, because the fully charged capacity is changed depending on SOH (State Of Health), temperature, etc., it is difficult to accurately detect SOC, taking into account those changes depending on time and environment as well.
To overcome such a difficulty, there are known techniques as follows. For example, JP-A-10-289734 (Patent Document 1) discloses that an initial battery characteristic is modified in accordance with a temperature modification coefficient computed based on a battery temperature and a deterioration modification coefficient computed based on a battery deterioration, and the remaining capacity of a battery is computed based on not only the modified battery characteristic, but also a discharge current and a terminal voltage during discharge.
Also, JP-A-11-218567 (Patent Document 2) discloses that a deteriorated battery characteristic is computed by modifying an initial battery characteristic based on respective relations to a temperature modification coefficient, an internal resistance deterioration modification coefficient, and a capacity deterioration modification coefficient.
JP-A-2000-166105 (Patent Document 3) discloses that the state of charge is detected based on a charge or discharge current, the state of accumulated electricity is detected based on a voltage, and the state of charge is controlled in accordance with the detected results.
JP-A-2000-166109 (Patent Document 4) discloses that an electromotive voltage is determined from a charge or discharge current and a voltage, and a charge characteristic is computed based on the relationship between the electromotive voltage and the charge characteristic.
Further, JP-A-2001-85071 (Patent Document 5) discloses that a temperature of each of combined battery modules is estimated based on a voltage between respective two terminals and a current flowing through each terminal.